The present invention relates generally to the data processing field, and more particularly, relates to a method and apparatus for identifying spindle imbalance in a hard disk drive.
Every facet of the E-commerce market is growing at a phenomenal rate. Most E-commerce systems consist of a computer system with one or more Redundant Arrays of Inexpensive Disks (RAID) storage systems. Almost all of the online catalogs and order/shipping data will be stored on RAIDs. These E-commerce systems are 24-hour-a-day, seven-day-per-week systems, and they have to operate at peak efficiency at all times. It is clear that such tremendous growth will demand the outmost of the computer systems supporting the worldwide E-commerce traffic reliably and expediently.
Modern disk drives are becoming more sophisticated with lower flyheight, higher areal recording densities, and faster rotational spindle velocities. One of the problems that arise in disk drive spindles is the spindle imbalance. This occurs when the center of gravity of the spindle does not coincide with the center of rotation. The net result is a mechanical sinusoidal vibration occurring at the fundamental spindle frequency. The causes for the spindle imbalance are many. Some of the most common imbalance-problems include mechanical tolerances in the bearings, the spindle shaft, and the disks; the mechanical assembly, like clamping and positioning, of the disk spindle; twisting of the disk enclosure while physically mounting the HDD in a RAID frame; the mechanical shocks caused in shipping of the HDD; slip or micro-creep of one or more disks during normal operation; age and wear of the mechanical structure, temperature cycling, and the like.
A spindle imbalance in a hard disk drive (HDD) causes mechanical vibrations in the disk drive enclosure and mounting frame. If this disk drive is situated in a RAID (Redundant Arrays of Inexpensive Disks), then the mechanical vibrations will disturb the neighboring HDDs and cause additional Track Mis-Registration (TMR) problems.
A need exists for a field upgradeable method that can screen HDDs for potential spindle imbalance problems before the drives are used, for example, in a RAID. Secondly, a need exists for a field upgradeable method to identify drives that develop the spindle imbalance problem during normal operation, so that such drives can be replaced or repositioned, to maintain peak performance of the E-commerce server system.
A need exists for an improved method and apparatus for identifying spindle imbalance in a hard disk drive.
A principal object of the present invention is to provide a method and apparatus for identifying spindle imbalance in a hard disk drive. Other important objects of the present invention are to provide such method and apparatus for identifying spindle imbalance in a hard disk drive substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, a method and apparatus are provided for identifying spindle imbalance in a hard disk drive. A position error signal (PES) is received from a plurality of sectors of a predefined cylinder for a plurality of disk surfaces. The PES is measured and stored for a defined number of revolutions for each of the plurality of disk surfaces. For each of the plurality of disk surfaces, a repeatable runout (RRO) of the PES is computed for the defined number of revolutions. A first harmonic discrete Fourier transform (DFT) and a first harmonic phase of the RRO are computed. Then a mean repeatable runout (MRRO) for the plurality of disk surfaces is computed. A first harmonic DFT and a first harmonic overall phase of the MRRO are computed. For each of the plurality of disk surfaces, cross-correlation coefficients are computed and summed to identify a spindle imbalance factor. The identified spindle imbalance factor is compared with a predefined threshold value to identify spindle imbalance in the hard disk drive.
In accordance with features of the invention, an available controller in the disk drive performs the method of the invention to identify spindle imbalance. In a Redundant Arrays of Inexpensive Disks (RAID) system, the RAID controller performs the method of the invention to identify spindle imbalance.